I received an invoice with negative "Total". What does this mean?

So far I only had an Apple Music subscription. Recently I started the trial for Apple One.

Few days ago was the due day for the Apple Music subscription, and I was charged.

Today I was charged for the Apple One subscription, as the trial has expired.

I received an invoice about the Apple One subscription payment, but along with it, I also received an Apple Music Subscription invoice, which had a negative "Total" amount in it.

What does this mean, am I about to be refunded?